In this paper，Au nanoparticles（Au NPs）/reduced graphene oxide（RGO） was used as the matrix of immunosensor to immobilize c reactive protein（CRP） antibody on the surface of glassy carbon electrode.A sandwich immunosensor was constructed using quinone dicarboxylic acid as tag.Under the optimal experiment conditions，the concentration of CRP was detected by differential pulse voltammetry.The linear range is 0.25-100 ng/mL with a detection limit of 0.08 ng/mL and a correlation coefficient of 0.997.This immunosensor provides a new simple means for the determination of c reactive protein.